Optoelectronic modules such as imaging cameras, proximity sensors, and range cameras include at least one optical element aligned to an active optoelectronic component (i.e., a component that either generates or is sensitive to a particular wavelength or range of electromagnetic radiation). The active optoelectronic component typically includes a photodiode or an array of photodiodes; a complementary metal oxide semiconductor (CMOS) or charge-coupled device (CCD) image sensor; or a laser diode or an array of laser diodes, such as a vertical surface-emitting laser (VCSEL) array. The at least one optical element (e.g., a refractive element, diffractive element, or microlens array) may be mounted within an optical housing. Moreover, the optical housing may be mounted to the active optoelectronic component, thereby providing a mechanical connection between the at least one optical element and the active optoelectronic component.
This broad class of optoelectronic modules can be integrated into myriad host devices ranging from portable electronic devices (e.g., smartphones, tablet computers, laptops, wearable electronics) to desktop computers and automotive systems. In many instances, the dimensions of these modules often strongly affect the dimensions of the host devices into which they are integrated.
For example, various components within an optoelectronic module, including an optical housing, can be aligned and mounted to an active optoelectronic component using a layer of adhesive. Typically, a significant amount of adhesive is used to provide a reliable mechanical connection and, in some cases, to provide a barrier to electromagnetic radiation, such as the particular range of electromagnetic radiation to which the active optoelectronic component is sensitive or operable to generate. In some instances, the adhesive layer also can isolate the active optoelectronic component from foreign matter, such as dust particles or humid air. Although the adhesive layer is effective, it is a viscous substance prior to curing and therefore tends to spread (e.g., onto sensitive areas of the active optoelectronic component). An adhesive overflow region may be incorporated into the optoelectronic module in the immediate vicinity of the active optoelectronic component to contain spreading adhesive thereby increasing the overall footprint (i.e., the x-, y-dimensions) of the optoelectronic module. Consequently, the dimensions of the host device into which the optoelectronic module is integrated are increased to accommodate the adhesive overflow region.
In addition to increasing the overall footprint of the optoelectronic module, the adhesive layer can cause additional problems. For example, the adhesive layer can absorb moisture after curing which tends to result in expansion. As the adhesive layer typically provides the mechanical connection between the active optoelectronic component and the optical housing (including the at least one optical element), moisture absorption can cause the active optoelectronic component and the at least one optical element to become misaligned. This effect is particularly pronounced for modules having thick adhesive layers.
A solution is needed that combines the functions of the adhesive layer as described in part above, but that does not significantly increase the footprint of the optoelectronic module and additionally resists misalignments due to moisture absorption.